Field of the Invention
The present invention relates to an information processing apparatus and an image processing apparatus, and a method of controlling the information processing apparatus, and more particularly to an information processing apparatus and an image processing apparatus that perform transmission and reception of data, and a method of controlling the information processing apparatus.
Description of the Related Art
Conventionally, there has been known an error control method that eliminates a reception error caused by a transmission error of packet data (hereinafter simply referred to as the “packet”) (see. e.g. Japanese Laid-Open Patent Publication (Kokai) No. S59-198039). More specifically, information processing apparatuses at respective transmitting and receiving ends transmit and receive packets according to the following protocol. First, the information processing apparatus at the transmitting end generates a packet to which a sequence number and an error correction code are added (set), on a predetermined data unit basis, transmits the generated packet to the information processing apparatus at the receiving end, and also holds the packet in a predetermined buffer provided in the information processing apparatus at the transmitting end. The information processing apparatus at the receiving end transmits a notification for requesting retransmission only with respect to a packet determined to have resulted in a reception error. In a case where a retransmission request notification is received from the information processing apparatus at the receiving end, the information processing apparatus at the transmitting end retransmits the corresponding packet held in the predetermined buffer in response to this request. Note that the sequence number represents the order of generation of a packet.
According to the above-described protocol, conventionally, in a case where the information processing apparatus at the receiving end suffers from a reception error of a packet, the information processing apparatus at the transmitting end retransmits the packet, thereby eliminating the reception error of the packet.
However, for example, in a case of occurrence of a reception error of a first packet whose sequence number is 1, noise can be sometimes superimposed on a signal of a retransmission request notification sent from the information processing apparatus at the receiving end. In this case, according to the error control method based on the protocol described in Japanese Laid-Open Patent Publication (Kokai) No. S59-198039, it is impossible for the information processing apparatus at the transmitting end to recognize the reception error of the first packet, so that the protocol for transmission and reception becomes ineffective.
More specifically, the information processing apparatus at the transmitting end recognizes that a reception error has not occurred with respect to the first packet whose sequence number is 1 because the above-mentioned retransmission request notification has not been received, and transmits a second packet whose sequence number is 2 as the next packet. On the other hand, although the information processing apparatus at the receiving end is waiting for the first packet, which is to be retransmitted, it receives the second packet, and hence the information processing apparatus at the receiving end determines that a reception error has occurred. Therefore, the information processing apparatus at the receiving end transmits the retransmission request notification again, but the information processing apparatus at the transmitting end retransmits the second packet in response to this request. As a result, deadlock in which retransmission of the packet and recognition of the reception error are repeated is caused between transmission and reception operations.
Here, according to Japanese Laid-Open Patent Publication (Kokai) No. S59-198039, the information processing apparatus at the receiving end sends the retransmission request notification (signal indicative of occurrence of a reception error) with respect to a packet determined to have caused a reception error to the information processing apparatus at the transmitting end. However, even when the information processing apparatus at the receiving end is configured to transmit a signal indicative of non-occurrence of a reception error to the information processing apparatus at the transmitting end in a case where a packet is correctly received, a similar problem of deadlock can be caused. Further, in a transmission and reception system provided in one information processing apparatus, for example, in an ASIC which performs image processing within an MFP, transmission and reception of a packet between a plurality of image processing modules within the ASIC, as well, can suffer from the similar problem.